Weight loss results from consistently consuming fewer calories than you use. Usually, you don't lose weight because you overeat and don't get enough physical activity. In some instances, a medical condition hinders weight loss. Your doctor can help design an effective strategy and determine whether a condition is partially to blame for an inability to lose weight.
You Eat When You Aren't Hungry
Perhaps you eat out of boredom, stress or emotional upset. If you take less than 20 minutes to consume a meal, your brain won't register satiety until well after you're full, says dietitian Joanne Larsen. Maybe you snack mindlessly while watching television, reading or surfing the web. Regardless, if you eat when you aren't hungry, it's difficult to lose weight.
You Take In More Calories than You Realize
Drinking beverages with calories throughout the day adds significantly to caloric intake. If you don't pay attention to calories and portion sizes, you can easily overeat. Meals from restaurants -- especially fast food establishments -- often contain far more calories than you'd expect. If you don't realize exactly how many calories you take in, you won't be able to lose weight.
You Skip Breakfast and Snacks
Besides providing energy for the day, breakfast keeps hunger at bay through the morning and early afternoon and quickens your metabolism. Breakfast and low-calorie snacks throughout the day help prevent excessive hunger that can prompt overeating at meals. If you starve yourself until lunch or dinner, you are more likely eat too much.
You Don't Get Aerobic Exercise
Aerobic exercise is the main way to burn calories for weight loss. Healthy adults should get at least half an hour of moderate to intense aerobic exercise a day. Though your basic bodily functions use calories all day long, if you're not burning extra calories with cardiovascular workouts, you're unlikely to lose weight, especially as your body adjusts to lower caloric intake.
You Don't Build Muscle
Muscle burns more calories more efficiently than fat, according to Sheri Barke, M.P.H., R.D., College of the Canyons nutrition coach. As you lose weight from eating less and increasing aerobic exercise, weight loss slows because at a lower weight you require fewer calories to maintain your body functions. This is called a plateau. You can restart weight loss by eliminating about 200 calories a day, as long as it does not put you under 1,200 calories, and adding or increasing resistance training to build muscle to keep weight loss efforts fruitful.
You're Retaining Fluids
Sometimes the body retains water, and hence water weight, with a condition called edema. Possible causes of edema include too much salt in the diet, medications, liver or kidney disease or damage, congestive heart failure, lymphatic system damage, venous insufficiency, and the menstrual cycle, pregnancy and other sources of hormone fluctuations, according to the University of Maryland Medical Center.
You Have an Underactive Thyroid
Hypothyroidism, or an underactive thyroid, can prevent weight loss and cause weight gain. It's typically diagnosed in people in their 40s and 50s, reports CNN. Other common symptoms include skin and hair problems, chronic fatigue, irregular periods, joint pain, muscle weakness and increased sensitivity to cold.
You Have a Hormone Imbalance
When the hormones that control weight are out of balance, you may not be able to lose weight. A number of things affect hormone levels, including medical conditions, pregnancy, medications and aging. Menstrual irregularities, skin and hair problems, acne, infertility and unexplained weight gain can indicate hormonal imbalances.
You Eat Foods Your Digestive System Doesn't Tolerate Well
Your body may not tolerate certain foods well. Though reactions to such foods aren't as serious as with an allergy, some foods cause fluid retention, affect your digestive system or energy levels and otherwise interfere with weight loss in some people. Various signs of digestive distress may indicate a problem. Food intolerance is a problem for about 10 percent of adults, CNN says.
You Take Certain Drugs or Supplements
Weight gain or inability to lose weight are side effects of some pharmaceuticals and supplements. Other side effects, such as edema, increased appetite and hormone imbalances, may be in play as well. Steroids, certain antidepressants and oral contraceptives are known to interfere with weight loss.